The invention relates to a device for turning sheet-like material, a printing unit, a multicolor rotary printing press, and in particular to a storage device for turning a sheet-like material, such as is used, for example, on a turning device on rotary printing presses.
Published, Non-Prosecuted German Patent Application No. 41 40 762 A1 relates to a sheet guide device. This sheet guide device can be used selectively for recto and verso printing, and through the use of this sheet guide device the sheet can be turned, in recto and verso printing, according to the principle of the turning of the sheet trailing edge. Pneumatically operating devices and mechanical devices are provided under the impression cylinder preceding the turning drum. In order to provide a sheet guide device through the use of which sheets can be guided and led, free of smudges, in the turning phase, without a sheet bunch being formed, the impression cylinder is assigned a guide doctor blade which can be acted upon pneumatically at a given angle of inclination and which is provided with individual air outlet orifices. After the impression cylinder grippers have been opened, the printed sheet is released from the impression surface of the cylinder by blowing air, steered under the guide plate and, by the emerging blowing air, both held up and transported in the direction of the transfer cylinder, until the turning drum conveys the sheet further on.
German Patent No. 44 24 967 C2 relates to a method and a device for sheet turning. It proposes a method for sheet turning in sheet-fed rotary printing presses capable of being changed over from recto printing to recto and verso printing, according to the principle of trailing edge turning, in which, in recto and verso printing, a print carrier sheet guided on a cylinder is picked up by a pivotable sheet take-over system of a turning drum following the cylinder, at the tangent point of the turning drum and cylinder, by the trailing edge, and is transported further on. At the tangent point, the start of the print carrier sheet is released by the sheet grippers of the cylinder and, immediately after the tangent point, is guided on a path deviating from the surfaces of the cylinder under the turning drum.
The storage of sheet-like material on the impression cylinders of a rotary printing press requires free space underneath the impression cylinder, so that the sheet-like material can be received over its entire length. Thus, the sheet can be picked up and turned by the turning drum, without coming into contact with machine parts, casings of transfer drums, guide plates or other sheets. The space required for storage is contrary to the requirement for the sheet-like material to be printed out during transfer in the recto printing mode onto the transfer drum following the impression cylinder. The sheet-like material has already left the printing nip during transfer in recto printing. Consequently, in printing units with a single-drum turning device, a complete length of the maximum processable printing format must be provided as a freely available sheet transport zone in each case both between the transmission cylinder and the central gripper assembly to a following transfer drum and between the following transfer drum and the central transfer assembly to the preceding transfer drum, the space for the collision of the fittings provided there being taken into account. Furthermore, the necessary space requirement for accessibility and for fittings upstream of the printing nip must also be taken into account.
A further possibility for solving the technical problem described is to pivot the configuration of the cylinders to an extent such that the construction space for printing out and for storage is gained at the expense of the fittings upstream of the printing nip. This measure is detrimental to the quality of sheet guidance upstream of the printing nip, so that the print quality obtained is poorer. Moreover, there is a fear of serious effects on the accessibility of the fittings. This makes it more difficult to clean, to carry out adjustments and to perform servicing during maintenance work.
A further remedial possibility is to restrict the permissible print carriers for the recto and verso printing mode to those papers which remain adhering to the circumference of the impression cylinder and do not move away from the impression cylinder as a result of a gravitational influence and flexural rigidity. Through the use of this measure the collision space to be kept free could be restricted and the permissible format length increased. The restriction to only some permissible print carriers for rotary printing presses with turning devices is seriously detrimental to the processable print carriers and can only be a compromise solution.
It is accordingly an object of the invention to provide a device for turning sheet material which overcomes the above-mentioned disadvantages of the heretofore-known devices of this general type and with which on the one hand, the format length of the sheet can be printed out completely and, on the other hand, the sheet-like material can be stored, completely free of collision, in the recto and verso printing mode, with the cylinder rolling conditions being maintained.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for turning sheet material, including:
an impression cylinder having an outer surface with a given curvature, the impression cylinder being configured to guide a sheet material received on the outer surface of the impression cylinder;
a first transfer cylinder preceding the impressing cylinder, the first transfer cylinder having an outer surface;
the impression cylinder and the first transfer cylinder defining a gusset region between the outer surface of the impression cylinder and the outer surface of the first transfer cylinder;
a second transfer cylinder following the impression cylinder; and
a throw-on device provided in the gusset region, the throw-on device contactlessly acting on the sheet material and causing the sheet material to assume, instead of a stretched position, a curved position corresponding to the given curvature of the outer surface of the impression cylinder such that a part of the sheet material is disposed in the gusset region.
In other words, according to the invention, a device for the turning of sheet-like material by use of a cylinder which guides sheet-like material and which is preceded by a transfer cylinder and followed by a transfer cylinder, the sheet-like material received on the outer surface of the impression cylinder being capable of being printed by a transmission cylinder, wherein, in the gusset of the outer surfaces between the impression cylinder and the preceding transfer drum, a contactlessly acting throw-on device is provided, which causes the sheet-like material to assume, instead of a stretched position, a curved position corresponding to the given curvature of the outer surface of the impression cylinder, with the gusset region being included.
Through the use of the throw-on device, configured and provided according to the invention, for the contactless holding of sheet-like, even relatively flexurally rigid sheet-like material, such as cardboard, the sheet-like material can be curved, free of smudges, onto the impression cylinder, so that no collisions of the ends of the sheet-like material, in particular when the latter assumes the stretched position, with fittings provided underneath the cylinders guiding sheet-like material and with the outer surface of the cylinders guiding the sheet-like material can occur. Through the use of the throw-on device proposed according to the invention, the tendency of relatively flexurally rigid sheet-like material, such as cardboard, to stretch out straight from a curved position can be counteracted. Through the use of the throw-on device proposed according to the invention, the involute peeling-off movement of the relatively flexurally rigid material away from the outer surface of the impression cylinder can be prevented. The fluid, for example blowing air, emerging from the contactlessly acting throw-on device is directed onto that region of the sheet-like material, such as paper or even relatively flexurally rigid cardboard, which is located just upstream of its trailing edge. The fluid emerging out of the throw-on device from outlet orifices includes at least one flow component which is directed perpendicularly to the desired position of the sheet-like material, that is to say points perpendicularly to the surface of the impression cylinder.
In an advantageous embodiment according to the invention, the contactlessly acting throw-on device generates, on the rear region of the sheet-like material, a force component which acts perpendicularly on the curved outer surface of the impression cylinder. What can be achieved thereby is that the rear end of the sheet-like material does not come to bear in its stretched position onto that outer surface of the impression cylinder which is located in the gusset region, but, instead, an additional length gain being produced.
The throw-on device may advantageously contain orifices, from which emerges a fluid, for example blowing air, in the form of free jets which have at least one flow component directed perpendicularly to the outer surface of the impression cylinder. The orifices may be formed on the contactlessly acting throw-on device either next to one another, one behind the other or in any other desired sequences. It is critical that a sufficient volume of a fluid can emerge through the orifices which generates the throw-on force acting perpendicularly to the outer surface of the impression cylinder.
In a first variant according to the invention, the throw-on device may be configured as a blowpipe embedded into the gusset region of outer surfaces of the preceding transfer cylinder and impression cylinder. The blowpipe may be positioned in a clearance between the outer surface of the preceding transfer cylinder and the sheet edge when the sheet-like material is in the stretched position.
In a further variant according to the invention, the contactlessly acting throw-on device can be integrated into a sheet guide device which is assigned to a preceding transfer cylinder. Consequently, the necessary construction space can be kept small and a fluid flow can be generated which lies as far as possible into the region of the central transfer point or transfer region between the preceding transfer cylinder and impression cylinder. The maximum format length of even relatively flexurally rigid material can thereby be widened, for turning, in such a way that the sheet end reaches almost as far as the central transfer point, without the risk of collision with the following sheet just being transported into the printing nip by the transfer drum and therefore without the risk of smudging.
According to another feature of the invention, the throw-on device acting contactlessly on the rear region of the sheet-like material includes outlet orifices, from which the medium generating the throw-on force emerges in such a way that the sheet edge of the sheet-like material is laid onto the outer surface of the impression cylinder with additional bearing contact, that is to say so as to achieve a curvature length gain, as far as below the central transfer point. The contactlessly acting throw-on device may advantageously be assigned a guide device which extends from a central transfer point between the outer surfaces of an impression cylinder and of a preceding transfer cylinder below the printing-unit cylinder as far as a further printing-unit cylinder or impression cylinder.
According to another feature of the invention, the guide device assigned to the contactlessly acting throw-on device may be formed in a curvature which is matched to the shape, precurved by the throw-on device, of the sheet-like material.
According to yet another feature of the invention, the guide device may be formed of individual rod-like or bar-shaped elements spaced from one another and preferably configured as round bars.
According to a further feature of the invention, the guide device may be configured as a continuous; in particular curved, guide plate.
In order to utilize the effectiveness of the throw-on device acting contactlessly on the rear region of relatively flexurally rigid sheet-like material for all formats which can be processed on a rotary printing press, the contactlessly acting throw-on device can be adapted, within an adjustment travel, to the sheet-like material to be processed in each case in the rotary printing press.
Particularly good gains in curvature length with regard to the bearing of the sheet-like material onto the outer surface of the impression cylinder are achieved when outlet orifices are provided at the upper end of the contactlessly acting throw-on devices, for free jets which flush separating air in between the printed side of the sheet-like material on the impression cylinder and the sheet on the transfer cylinder preceding the latter. It is thereby possible to prevent the still unprinted surface of the following sheet from adhering to the already printed outward-facing surface of the sheet-like material printed on one side.
On that side of the contactlessly acting throw-on device which faces the outer surface of the impression cylinder, outlet orifices can be provided, through which the free jets generating the holding force can be guided, in order to produce a curvature length gain, into the gusset region between the impression cylinder guiding the sheet-like material and the transfer cylinder preceding the impression cylinder.
According to another feature of the invention, a transmission cylinder is provided adjacent to the impression cylinder for printing onto the sheet material.
The device, proposed according to the invention, for allowing collision-free turning of even relatively flexurally rigid sheet-like material can be used preferably in printing units of sheet-processing rotary printing presses configured as an inline construction, in particular on multicolor rotary printing presses, in which a sheet turning device is received.
With the objects of the invention in view there is therefore also provided a printing unit, including:
a turning device for turning a sheet material, the turning device including an impression cylinder having an outer surface with a given curvature, the impression cylinder being configured to guide the sheet material received on the outer surface of the impression cylinder, a first transfer cylinder preceding the impressing cylinder, the first transfer cylinder having an outer surface, the impression cylinder and the first transfer cylinder defining a gusset region between the outer surface of the impression cylinder and the outer surface of the first transfer cylinder, a second transfer cylinder following the impression cylinder, and a contactlessly acting throw-on device provided in the gusset region, the throw-on device causing the sheet material to assume, instead of a stretched position, a curved position corresponding to the given curvature of the outer surface of the impression cylinder such that a part of the sheet material is disposed in the gusset region; and
a transmission cylinder provided adjacent to the impression cylinder for printing onto the sheet material.
With the objects of the invention in view there is further provided a multicolor rotary printing press, including:
a turning device for turning a sheet material from a printed side onto a side to be printed, the turning device including an impression cylinder having an outer surface with a given curvature, the impression cylinder being configured to guide the sheet material received on the outer surface of the impression cylinder, a first transfer cylinder preceding the impressing cylinder, the first transfer cylinder having an outer surface, the impression cylinder and the first transfer cylinder defining a gusset region between the outer surface of the impression cylinder and the outer surface of the first transfer cylinder, a second transfer cylinder following the impression cylinder, and a contactlessly acting throw-on device provided in the gusset region, the throw-on device causing the sheet material to assume, instead of a stretched position, a curved position corresponding to the given curvature of the outer surface of the impression cylinder such that a part of the sheet material is disposed in the gusset region; and
a transmission cylinder provided adjacent to the impression cylinder for printing onto the sheet material.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a storage device for the turning of sheet-like material, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional object""s and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.